There exists a need in motion control applications for the use of step motors as through-hole motors in semiconductor, manufacturing and medical processes that use light emitted by lasers, radar positioning pedestals, and environmentally controlled chambers. Current step motor designs do not easily adapt to such through motor applications without substantial modification.
One example of a motor having an internal opening is found in U.S. Pat. No. 4,646,689 entitled "Engine Intake Passage Length Varying Device" wherein a cylindrical rotor is mounted co-axially with a hollow chamber that contains the air filter of an automotive engine.
U.S. Pat. No. 4,280,072 entitled "Rotating Electric Machine" and U.S. Pat. No. 5,369,324 entitled "Electric Stepper Motor" both describe highly efficient rotor and stator configurations to provide enhanced motor torque.
The state-of-the-art stepper motor designs do not readily allow motors to be stacked end-to-end for multi-axis motion nor allow passage of electric wires or air passage through the center of the motors. Such motors do not readily allow field conversion from a rotary to lineal actuator without substantial modification to the mounting structure.
One purpose of the invention is to describe a stepper motor having means for passage of wires and the like through the center of the motor along with improved motor torque efficiency. The motor includes means for conversion from rotary to lineal actuation with only minor modification to the motor mounting structure.